Estimation of cereal yields combining crop growth models and remotely sensed vegetation indices

A cereal yield estimation system has been developed that incorporates a crop growth model and satellite vegetation indices to estimate areas and yields of wheat and barley at agricultural district level, every month throughout the growing season. The agro-meteorological model simulates biomass accumulation through numerical integration with a daily time-step. Growth is taken as the minimum of water limited growth, calculated from potential water uptake rates and the amount of available water in the rooting zone, and light limited growth, calculated from the fraction of photosynthetically active radiation intercepted by the leaves. The link between this yield model and information from satellite images is founded on the assumption that there is a relationship between the vegetation index derived from the image data and the green leaf area index used in the model. To find the best fit between the model and the image data an optimisation process is used.